1. Field of the Invention
This invention relates to spray systems and more particularly to airless spray systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Painting is a very labor intensive endeavor and costs are primarily a function of the painter labor cost. Thus, it is important to increase the productivity of painters as much as possible.
There are a number of ways to paint a surface, such as a wall, structure or house. One conventional approach is to use paint brushes; however this is prohibitively expensive for large structures, because the painter can only apply paint at a rate which is determined by the width of the brush and it is necessary to continuously dip the brush into paint to rewet the brush. One conventional approach that speeds paint application is to use a paint roller; however, this has also proven to be relatively costly for painting large structures and has the same shortcoming that the roller must be continually rewetted with paint.
A conventional approach that does not need continual pausing to rewet a brush or roller is to use an airless spray system, which can be used to spray paint and other fluids. An airless spray system consists of a pump that pressurizes paint drawn from a tank to about 2500 pounds per square inch. The pressurized paint is sent through a high pressure hose to a spray gun with a single spray tip nozzle, which has a trigger controlled by the painter. The painter points the spray gun at the surface to be painted, activates the spray gun trigger, and moves the spray gun in a sweeping motion covering the surface with paint. The speed at which the painter can move the fan of paint spray across the surface is a function of the amount of paint that must be applied and the width of the fan beam of paint spray from the single spray tip nozzle.
There is a numbering system for spray tips, which are nozzles placed on the spray gun, that indicates the width of the fan beam and the size of the opening in the nozzle. The width of the fan beam is the width of the paint spray fan beam on a surface one foot from the spray gun nozzle. The size of the opening in the nozzle indicates the paint flow rate from the spray tip. A larger size opening in a spray tip increases the paint flow rate that exits the opening.
For example, a 513 spray tip has a nominal fan beam width of 2 times 5=10 inches at a foot away from the surface and has a 0.013 inch size opening. A 515 spray tip has the same fan beam width as a 513; however, a 515 has a larger opening and therefore the paint flow rate will be higher. A 619 spray tip has a nominal 12 inch fan beam width when spraying 12 inches from the surface and a nozzle opening of 0.019 inches. The painter selects a spray tip that is appropriate for each type of painting. A 619 spray tip may be appropriate to paint a large concrete wall; however, a 513 spray tip may be more appropriate for painting fine furniture.
With the conventional single spray tip apparatus, one approach to increasing the width of the fan of paint spray is to select a spray tip with a larger fan beam; however, in general spray tips all have approximately a one foot wide spray beam. Also, a spray tip with a larger fan beam, such as a 619 spray tip versus a 513 spray tip, may not be appropriate because the spray tip with the larger fan beam may have a flow rate that is too large. A larger size opening in a spray tip increases the paint flow rate; however, the painter does not have as much control with a larger opening as with a smaller opening.
Another approach to cover a larger area with the conventional apparatus is for the painter to hold the spray gun further away from the surface being painted. For example, if a 513 spray tip is held about 3 feet away from the surface, then one would expect that the fan beam would triple to about 30 inches in width; however, the disadvantage of increasing the spray width by holding the spray gun further away from the surface is that more of the paint atomizes and dries in the air and therefore does not reach the surface to be painted, thereby reducing the volume of paint on the surface. This wastes paint and actually slows down the painter, because to obtain the proper volume of paint on the entire surface, the painter will have to move the spray gun slower. Therefore, moving back from the surface is not a solution to increasing the fan beam width and thereby the productivity of the painter.
Another approach to cover a larger area with the conventional apparatus is to use a dual spray nozzle, which is a device that has two spray nozzles immediately adjacent to the spray gun. In one device the nozzles can swivel 90 degrees from center. For example, the two spray nozzles can be swiveled to 30 degrees off center, which would cover a larger area than a single nozzle. However, the shortcoming with this design is that there is too much paint sprayed near the center of the larger spray fan beam and not enough paint sprayed at the two ends of the spray fan beam. Also, the painter would have less control of the painting due to the unevenness of the spray fan beam.
The conventional spray gun, while an improvement over paint brushes and paint rollers, still limits the productivity of painters.
Accordingly, there is a need in the art for a paint spray system and approach that reduces the cost of spray painting with an airless spray system and increases productivity, while maintaining an even spray fan beam.